#include <iostream>
using namespace std;

const double N = 100, eps = 10e-8;
double n, ans;

bool check(int ans, int n)
{
    return ans ^ 3 <= n;
}

int search(double n, double l, double r)
{
    double mid = (l + r) / 2;
    while (r - l > eps)
    {
        if (check(mid, n))
            l = mid;
        else
            r = mid;
        mid = (l + r) / 2;
    }
    return r;
}

int main()
{
    scanf("%lf", &n);
    ans = search(n, -N, N);
    printf("%.6lf", eps);
    return 0;
}